This proposal investigates at the molecular level the role of the human papillomavirus type 16 (HPV16) transforming gene products E6, E7, and E5, in combination with changes in the expression of epidermal growth factor receptor (EGFR) and transforming growth factor-alpha (TGF-alpha), in the following two initial steps of HPV16-mediated human cell carcinogenesis in vitro: 1. HPV16-induced immortalization of normal human keratinocytes (HKc), and 2. The subsequent acquisition of growth factor-independence (GFI) in cell lines (HKc/GFI) selected from the HPV16-immortalized HKc (HKc/HPV16) by culture in the absence of epidermal growth factor (EGF) and bovine pituitary extract (BPE). In the in vitro model for HPV16-initiated human carcinogenesis used in these studies, malignancy is achieved through at least four reproducible and phenotypically-defined """"""""steps"""""""": immortalization, GFI, differentiation-resistance, then malignant conversion. Preliminary data indicate that changes in EGFR and TGF-alpha (a ligand for the EGFR) expression play an important role in both the immortalization and the GFI step: EGFR mRNA expression is consistently increased in HKc/HPV16 compared to their parental normal HKc. EGFR numbers are further increased in HKc/GFI compared with HKc/HPV16, with no additional increase in EGFR mRNA levels. EGFR in HKc/GFI (but not HKc/HPV16 or normal HKc) are tyrosine-phosphorylated in the absence of EGF. HKc/HPV16 and HKc/GFI overexpress TGF-alpha mRNA by about 4-fold over normal HKc, but secrete into the medium about 100-fold less mature TGF-alpha. In addition, HPV16 E5 is required for the acquisition of the GFI phenotype. In these proposed studies defective retroviruses expressing single HPV16 open reading frames (ORFs: E6, E7, and E5) or the EGFR will be used to infect normal HKc, to investigate the role of each ORF, as well as the interactions o the viral oncoproteins with the EGFR and TGF-alpha genes that lead to immortalization and GFI. The role of E5 at the GFI step will also be investigated. The turnover, tyrosine kinase activity, phosphorylation state, and dimerization of the EGFR in HKc/GFI, in comparison with their parental HKc/HPV16 lines, will be studied. EGFR- mediated signal transduction in the context of HPV-initiated transformation will be investigated. Changes in TGF-alpha processing in HKc/HPV16 and HKc/GFI which may contribute to the GFI phenotype, and factors that may determine these changes will also be studied. Taken together, the results of this work will help clarify the mechanism of HPV16-mediated human carcinogenesis, and tumor progression in general.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA062094-02
Application #
2330855
Study Section
Virology Study Section (VR)
Project Start
1996-04-01
Project End
2001-01-31
Budget Start
1997-02-01
Budget End
1998-01-31
Support Year
2
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of South Carolina at Columbia
Department
Pathology
Type
Schools of Medicine
DUNS #
111310249
City
Columbia
State
SC
Country
United States
Zip Code
29208
Akerman, G S; Tolleson, W H; Brown, K L et al. (2001) Human papillomavirus type 16 E6 and E7 cooperate to increase epidermal growth factor receptor (EGFR) mRNA levels, overcoming mechanisms by which excessive EGFR signaling shortens the life span of normal human keratinocytes. Cancer Res 61:3837-43
Xu, X; Kelleher, K F; Liao, J et al. (2000) Unique carboxyl-terminal sequences of wild type and alternatively spliced variant forms of transforming growth factor-alpha precursors mediate specific interactions with ErbB4 and ErbB2. Oncogene 19:3172-81
Borger, D R; Mi, Y; Geslani, G et al. (2000) Retinoic acid resistance at late stages of human papillomavirus type 16-mediated transformation of human keratinocytes arises despite intact retinoid signaling and is due to a loss of sensitivity to transforming growth factor-beta. Virology 270:397-407
Mi, Y; Borger, D R; Fernandes, P R et al. (2000) Loss of transforming growth factor-beta (TGF-beta) receptor type I mediates TGF-beta resistance in human papillomavirus type 16-transformed human keratinocytes at late stages of in vitro progression. Virology 270:408-16
Xu, X; Liao, J; Creek, K E et al. (1999) Human keratinocytes and tumor-derived cell lines express alternatively spliced forms of transforming growth factor-alpha mRNA, encoding precursors lacking carboxyl-terminal valine residues. Oncogene 18:5554-62
Khan, M A; Canhoto, A J; Housley, P R et al. (1997) Glucocorticoids stimulate growth of human papillomavirus type 16 (HPV16)-immortalized human keratinocytes and support HPV16-mediated immortalization without affecting the levels of HPV16 E6/E7 mRNA. Exp Cell Res 236:304-10